1. Field of the Invention
The present invention generally relates to a communication system and, more particularly, to a connection close-related packet transmission method and apparatus for improving power saving efficiency of a power-constrained mobile terminal in the communication system.
2. Description of the Related Art
Typically, a mobile device using wireless communication networks is capable of supporting Transmission Control Protocol (TCP) for data transfer applications such as a web browser.
In Hypertext Transfer Protocol (HTTP)/1.0, if the request/response exchange ends between a client and a server, the TCP connection for exchanging the request/response is closed. However, HTTP/1.1 supports HTTP persistent connection. In HTTP/1.1, if data transfer is further required after the initial request/response exchange, it is possible to exchange the request/response to continue data transfer in the same TCP before the connection close timeout preconfigured for connection closes. This means that the 3-way handshake process for establishing/releasing a TCP connection is omitted so as to improve HTTP performance. The 3-way handshake is performed in the order of SYN→SYN+ACK→ACK. A detailed description thereof is made later with reference to FIG. 1.
Recent mobile devices such as Android smartphones mostly support HTTP/1.1 to improve the loading speed of a webpage. When transmitting and receiving data for web browsing through the HTTP persistent connection by means of a power-constrained mobile device, it is possible to reduce the time consuming process of TCP connection setup/release, resulting in improvement of mobile device performance. The HTTP server may transmit a message including an explicit parameter “connection: close” in the header such that the client starts releasing the connection. However, the explicit parameter is likely to be excluded by taking notice of the HTTP persistent connection characteristics.
FIG. 1 is a message flow diagram illustrating the conventional TCP connection establishment and release procedure.
A terminal 100 sends a Synchronization (SYN) packet to a first server 102 at step 110. The first server 102 sends a SYN Acknowledgement (SYN+ACK) packet to the terminal 100 in response to the SYN packet at step 115. The terminal 100 sends an ACK packet to the first server 102 in response to the SYN+ACK packet at step 120. Thus, the 3-way handshaking consists of steps 110 to 120. If the 3-way handshaking has been completed, a connection is established between the terminal 100 and the first server 102 at step 125. Afterward, the terminal 100 and the first server 102 communicate data at step 130. The connection activity ends at step 135. The connection activity is the activity of exchanging data through the connection established at step 125.
Afterward, the terminal 100 monitors to detect the connection activity before the expiry of a connection close timeout 190 and sends, if no connection activity is detected before the expiry of the connection close timeout 190, a Finish (FIN) packet to the first server 102 at step 140. The first server sends an ACK packet to the terminal 100 in response to the FIN packet at step 145.
Afterward, the terminal 100 may perform the 3-way handshaking with a second server 104 through steps 150, 155, and 160. As a result, the terminal 100 and the second server 104 establish a connection at step 165.
When the message includes no “connection: close”, the client monitors to check the connection activity before the expiry of the connection close timeout set for the HTTP connection close. If the connection close timeout expires without connection activity, the FIN/ACK packets act as the control messages for releasing the TCP connection, and are exchanged at steps 140 and 145. In the meantime, the radio communication module in charge of transmitting/receiving data enters a power saving mode after an inactivity timeout. In the conventional method, the radio communication module stays in an active state unnecessary until the control message (FIN/ACK) exchange for release of the TCP connection is completed after the expiry of the connection close timeout, resulting in an unnecessary waste of battery power.
FIG. 2 is a graph illustrating packet transmission amount in loading an Internet webpage in the conventional method. In the graph of FIG. 2, the horizontal axis denotes time, and the vertical axis denotes number of packets.
FIG. 2 shows that the FIN packet occurs at 5 to 10 seconds after the last data transmission/reception as denoted by reference number 210. If the radio communication module enters the power saving mode without transmitting the FIN packets, it is possible to reduce the unnecessary power consumption.